Various specialized medical devices, such as cardiac leads, ablation catheters, electrophysiological diagnostic catheters, pressure monitoring catheters etc., require the use of a delivery system for deploying the device in a desired internal body space, such as the heart or vascular system. Delivery systems commonly include a steerable guide catheter. The guide catheter may be steered to a desired internal body location allowing a medical device to be deployed at a desired site through a central lumen of the catheter. Other types of medical therapies, such as genetic, biologic, or pharmacological agents, may require local administration through a delivery catheter. An implant or therapy delivery site generally needs to be carefully selected in order to achieve a desired therapeutic effect. Typically the location of a guide catheter within a patient's body is determined by taking a fluoroscopic image during the procedure. Multiple fluoroscopic images may be needed during a single procedure in order to follow the progress of a guide catheter as the guide catheter is advanced within the patient's body.
In order to avoid repeated exposure of the patient and operating room staff to ionizing fluoroscopic radiation, navigable guide catheters have been proposed that are equipped with location sensors for determining the location of a guide catheter within the patient's body. Locatable or navigable guide catheters are generally disclosed in U.S. Pat. No. 5,042,486 issued to Pfeiler et al., U.S. Pat. No. 5,592,939 issued to Martinelli, U.S. Pat. No. 6,253,770 issued to Acker et al., and U.S. Pat. No. 6,210,362 issued to Ponzi et al. One type of location sensor is an electromagnetic coil in which current is induced by an externally applied electromagnetic field. The location of the sensor coil relative to the external field source is determined from the measured current.
Image guided medical and surgical procedures utilize patient images obtained prior to or during a medical procedure to guide a physician performing the procedure. The location of a navigable catheter may be displayed on an image of the navigation domain taken prior to a procedure. An image guided catheter navigation system that enables the physician to see the location of a catheter relative to a patient's anatomy, without the need to acquire real-time fluoroscopic images is generally disclosed in co-pending U.S. patent application Ser. No. 10/299,969 to Hunter et al., entitled “Navigation System for Cardiac Therapies”. In this system, it is desirable to locate and display a distal segment of the catheter rather than a single point such that navigation of the catheter is more intuitive to the physician. Therefore, it is desirable to include multiple location sensors along a segment of the navigable guide catheter. A system for navigating a catheter within a navigational domain including a catheter having locatable electrode elements distributed along and affixed to a length of the catheter is disclosed in U.S. Pat. No. 6,104,944 issued to Martinelli.
It may be further desirable to provide additional components along the catheter body such as stimulating or sensing electrodes or other types of physiological sensors to allow physiological signals to be monitored for diagnostic purposes or for selecting a therapy delivery site during advancement of the catheter. Thus it is desirable to provide a navigable guide catheter having multiple lumens for carrying multiple conductors between a proximal end of the catheter and multiple location sensors and any other optional sensors or electrodes that may be present in addition to providing an open lumen through which a medical device may be deployed or medical therapy may be administered.
Guide catheters are sometimes provided with reinforcing braiding within the wall of the catheter body. Such reinforcing braiding promotes kink resistance and can improve the amount of torque transferred between the proximal and distal end of the catheter. Efficient torque transfer is often desirable in catheter bodies to improve handling of the catheter as the catheter is steered along a desired pathway. A limitation of such braiding is that, when the braiding is formed from a metallic material, the braiding may interfere with the performance of electromagnetic location sensors by shielding the sensors from an externally applied electromagnetic field. However, the magnitude of the shielding effect is relative, and therefore some systems may work with braided shafts. Factors affecting the degree of shielding include the braid configuration, the receiver coil sensitivity and the source field strength. If the braid does extend over the receiver coil but is terminated before the coil, the braiding may not interfere with the location sensor function. However, it is desirable to provide a multilumen catheter body that provides good kink-resistance, variable stiffness, and efficient torque transfer without the incorporation of reinforcing braiding.
Multipolar medical leads may also employ a multilumen body for carrying multiple conductors between a proximal lead end and electrodes located along the lead body or at a distal end of the lead body. Cardiac leads having three, four, or more electrodes may be used for sensing cardiac signals and for delivering stimulation in the form of pacing, or cardioversion or defibrillation shock therapy. Multipolar leads may also be used for sensing and stimulating at multiple sites within the heart. Cardiac leads generally need to be highly flexible in order to withstand continuous flexing motion caused by the beating heart without fracturing. A stiff stylet advanced through a lumen of a lead body provides a flexible lead with the stiffness needed to advance the lead through a venous pathway. Leads may also be advanced over a guidewire, sometimes referred to as “over-the-wire” leads, however, a guide catheter is still often used during the placement of an “over-the-wire” lead for backup support and also because the flexible lead body may not have sufficient torque transfer from its proximal to distal end to allow the lead body to be rotated as the lead body is advanced through a venous pathway and fixed at a final location. Guide catheters, and particularly guide catheters having reinforcing braiding material within the catheter walls, provide effective torque transfer that may be needed for advancing and fixing a lead. However, during the implantation procedure the size of the guide catheter may limit the ability to advance a small diameter lead into narrow locations, such as within the cardiac veins. It is therefore desirable to provide a multilumen lead body having a desired degree of torque transfer from its proximal to distal end and the flexibility needed to withstand repeated flexion.
Multilumen lead bodies are generally formed as a multilumen extrusion. One multilumen lead body is described in U.S. Pat. No. 5,584,873 issued to Shoberg et al. In order to assemble a multipolar lead employing a single extruded multilumen body, each conductor for each electrode is threaded through a lumen of the lead body one at a time. As the number of electrodes and associated conductors increases, and as lead bodies are reduced in size to allow for easier implantation within a patient's vessels, the task of threading each conductor through its respective lumen can become tedious and time consuming. It is desirable, therefore, to provide a multilumen body that allows assembly of multiple conductors within the body to be performed quickly and easily.
What is needed therefore, is an improved multilumen elongated body for use with medical catheters or leads that is kink-resistant, allows for a desired degree of torque transfer from its proximal to distal end without reinforcing braiding material, and multiple conductors to be readily assembled within the multilumen body.